The invention relates to a sleeve formed of a shrinkable material sleeve body having a longitudinal closure with projections and corresponding cut-outs along both opposite longitudinal edges. The projections and cut-outs of the two longitudinal edges are offset relative to one another and can be inserted one into another.
British Pat. No. 1,506,242, incorporated herein by reference, has disclosed a heat-shrinkable sleeve which, along both longitudinal edges, is provided with projections, is undercut in dove-tailed fashion, and has matching cut-outs for longitudinal closure. When the sleeve is assembled, the individual projections are inserted into the opposite cut-outs so that they are hooked one to another. However, this method of hooking has various disadvantages. On the one hand, the sleeve can relatively easily snap open when heated, unless it is ensured that relatively thin longitudinal edges are appropriately fixed, and on the other hand in the case of thin wall thicknesses, which are usual in the case or film-type sleeves, a closure of this kind cannot be achieved since it is scarcely possible to hook the thin closure elements one to another. Therefore, in this cable sleeve, a so-called "underlay" is provided which contributes to the support of the closure elements. This means that a continuous and thus cost-saving production process--such as for example an extrusion--is impossible, or difficult to achieve. Furthermore, the stability of the closure during the shrinkage process is an extreme problem since the shape stability can be ensured during the necessary heating only by means of an extremely high cross-linking. In such a case, the expansion factor is then impermissibly limited for most applications.